LAS VEGAS – In May, Knicks president Isiah Thomas flew to Los Angeles. Some thought Thomas was there to conduct a second interview with Phil Jackson.

Not the case. Thomas was seeking to interview Paul Westphal. A former NBA head coach, Westphal had flown under the radar the past four years, coaching in the shadow of UCLA and USC, at Pepperdine in the West Coast Conference.

Saturday night, during NBA summer league play at UNLV, Knicks interim coach Herb Williams and Westphal sat together in the third-to-last-row of the bleachers, the latest bombshell in the Knicks’ coaching search that has been going on for three months.

Thomas, who interviewed Westphal for the head-coaching position, is now looking at the former Sonics and Suns head coach as the perfect top assistant for Williams, who clearly will be the Knicks’ head coach next season if Larry Brown stays in Detroit. And, of course, if Williams doesn’t make it through the season, Westphal, if hired as an assistant, would be waiting in the wings.

According to a person familiar with the coaching search, Williams, upon Thomas’ urging, interviewed Westphal for two days here during summer-league play. As reported in The Post on Sunday, the rendezvous culminated Saturday night as Williams and Westphal sat together for more than three hours in animated discussion watching two summer-league games, including the Knicks against the Wizards. Westphal flew back to Pacific Palisades, Calif., yesterday. One of Westphal’s friends said he had “a nice time” meeting with Williams.

Williams has declined comment, as has Westphal. The Knicks are mum, but contend Williams has not been offered the job yet. A league source says the Knicks will still monitor the Brown soap opera, even if his wife, Shelly Brown, has told Thomas to move on because her husband will be returning to Detroit. The Pistons publicly have been less emphatic on the topic and there’s speculation Brown could still be fired.

And Bill Laimbeer’s candidacy has been blown to bits.

Westphal has spent four seasons at Pepperdine. Westphal compiled a 294-181 record for the Suns and Sonics, who fired him in 2000-2001 after a verbal jousting with Gary Payton. Westphal’s NBA winning percentage of 61.9, including playoff games, is ranked highest in the league. Thomas loves his offensive mind.

However, the stigma of Westphal’s firing in Seattle remains a concern. The Sonics let him go, saying the team’s defensive approach was lacking and he was tagged for being too easy-going with Payton.

After firing Westphal, Sonics president Wally Walker said, “At the end of the day our problem was, we didn’t defend well enough.”

And when Nate McMillan was promoted, he took a shot at Westphal, the laid-back Californian. “Players tend to take people’s niceness and abuse it,” said McMillan. “We’re going to change some things.”

Some players weighed in, too.

“We have no team defense,” Desmond Mason, then with the Sonics, said after Westphal’s firing. “We have some of the best one-on-one defenders in the league, but our concept of team defense is very weak right now.”

The Knicks’ biggest problem last season was defense, but with the slate of athletic new players, Thomas may be looking for Westphal, if hired, to be the offensive coordinator and allow Williams to handle the defense.